Hi , you can try to change the patch cable between the PoE adapter and the Gateway. Please check that LAN cable is fully 8 pin (there are only 4 pins in the market). I assume that the Gateway is opened (if you can check the LEDs) so please try to plug it directly to the PoE patch cable without the LAN gland.

Hi,
I used working LAN Cable and also i checked with different working LAN Cables.
I did the same as you mentioned like plugging the PoE Patch cable without the LAN gland also.
Still, the gateway won’t powered-up.

With the patch cable plug in the PoE port of the PoE adapter(powered) you can measure the output voltage (around 48Volts). The possitive pins are 4 and 5, negative are 7 and 8. You can see all pins here (Pinouts table) https://en.wikipedia.org/wiki/Power_over_Ethernet

If the POE circuit is normal,the gateway will be powerd up(But in fact it will not because it has issues).

No need as you have said that Power issue resolved with 12V 2A Power adapter.I just want to judge the issue point is before PD IC or after PD IC(48V to 12V convert circuit).If it’s before PD IC,maybe we still have chance to resolve it(Remove D2 and try PoE again).If not,Lets go Return Material Authorization process.